WIP Gateway Application : can I firewall?


Good day

I have lots of Wavecome Supreme 20’s and Xtend’s fitted with Ethernet IESM’s that I now I have dusted them off and use as Internet Gateways . Well I have re-fitted them all with the formware ver 7.46.6 and compiled the Internet Gateway app . Great app ! I am using DHCP on ethernet and DNS proxy .

Ok , now I want to use them as gateways only to MQTT cloud servers TCP port 1883 , example

Question , is it possible to forward only a specific port thru the NAT / IP Forward machinery of WIP ? If not , can I somehow use the TUP tunnel to intercept and manually pass traffic programmatically ? Good info of TUN/TAP seems to be in short supply.

In general terms , can I entertain port firewall in any manner ?